1. Field of the Invention
This invention relates generally to a power transfer mechanism adapted to be incorporated in a multiple path drive system, for example a four-wheel drive vehicle. More particularly, it relates to a torque transfer case adapted to receive torque from a prime mover and to provide torque for one drive axle where two-wheel drive is adequate, and to provide torque for both drive axles automatically where four-wheel drive is required. The torque transfer case incorporates a double-acting roller clutch responsive to relative rotation between the drive axles for automatically engaging where four-wheel drive is required.
2. Description of the Prior Art
In recent years there have been many improvements in automotive drive trains, including improvements relating to the transfer of torque from a prime mover to drive axles. Where four-wheel drive systems are used, transfer cases have been developed which generally provide torque transfer to one output to drive an axle and to another output for driving another axle. Some such transfer cases generally have included a free wheel mechanism which automatically engages and disengages the four-wheel drive function. These mechanisms generally have incorporated a biasing feature wherein friction drag to ground is developed. However, this friction drag is affected adversely by centrifugal force. Separate torque transfer cases have been required for establishing each torque transfer path desired. Transfer cases have been developed for providing torque transfer from an input to one output coaxial therewith and another output offset therefrom. Other transfer cases have been developed for providing torque transfer from an input to a pair of offset outputs.